ighty Zeus brings Hercules' mother, Alcmene, to Mount Olympus, and Hercules, believing she has been kidnapped, leads a rescue mission to save her. Zeus' jealous wife, Hera, decides that it should now be her time to rule the universe. Hera steals the Chronos Stone, source of the God's power, and unleashes the four Titans from their eons of imprisonment. With these angry behemoths on the loose, only the combined forces of Hercules and Xena, together with their trusty sidekicks Iolaus and Gabrielle, can save Mount Olympus.

Overview from themoviedb.org